The present invention relates to a method for weaving a webbing comprising a right-hand weft thread (SFR) and a left-hand weft thread (SFL), it also relating to a narrow fabric needle loom.
Known from DE 27 19 382 C3 (Berger) is weaving a single-ply seat belt webbing having tubular selvedges on a narrow fabric needle loom by a sole weft needle. One of two single-ply woven edge portions is pulled up to the selvedge of the middle portion to form the one tubular selvedge by pulling the weft thread.
Known from CH 648 069 A5 (Berger) is a webbing particularly for automotive seat belts made on a narrow fabric needle loom. The webbing features a relatively stiff middle portion and soft edge portions formed into tubular selvedges. To speed up production two weft needles are provided working simultaneously in parallel, the one picking a soft weft thread in the middle portion and the two edge portions, the other picking a stiffer weft thread in just the middle portion and picking only the two outermost warp threads of the two edge portions. Two weft needles pick simultaneously two different weft materials into partly different shed openings. The two flat edge portions are drawn into tubular selvedges by the one weft thread picked only via the middle portion. The middle portion is reinforced to achieve a higher performance. The aim was to double the output by using two weft needles as compared to single needle systems. However, the larger mass and the needed larger and faster movements of the auxiliary pickers resulting from the two weft needles only made it possible to achieve much less than twice the output.
Known from DE 33 45 508 C2 (leperband) is a webbing (safety belt) woven single-ply, likewise making use of two weft needles simultaneously to pick two different weft yarns. A monofil weft thread merely serves to reinforce the middle portion and must not be used to pull over the flat edge portions. By current standards these known webbings and methods of their production are too costly and have since ceased to satisfy the increasing demands of the automotive industry. What has particularly increased are the demands on webbing having comfortable soft edge portions whilst the inner portion is required to feature maximized transverse stiffness. On top of this, these known devices for producing webbing are very complicated and difficult to master in operation.
It is thus the object of the present invention to propose a webbing, a method and a narrow fabric needle loom of the aforementioned kind which now avoids or at least greatly minimizes the drawbacks of prior art. This object is achieved by a method as set forth in claim 1, namely a method for weaving a webbing comprising a right-hand weft thread and a left-hand weft thread, characterized in that the two weft threads are picked into the same shed from both sides of the seat belt webbing, are wound around weft holdbacks in weft reversal loops, are substantially retained by the weft holdbacks until beat by the reed against the fell, it not being until then that a shed change is made. This technique in accordance with the invention results in two weft threads each coming simultaneously from the right-hand and left-hand weft picking side being picked practically symmetrically transversely over the webbing where they are each held back at the opposite side by a separate weft holdback provided there, after which the weft needles are retracted to their side thereby entraining the weft thread and holding it taut until the reed has beaten up the freshly picked weft threads to the already woven webbing material, the weft threads being held back up to this point in time by the weft holdbacks being set by the advanced shed change.
In this arrangement the webbing is advantageously produced without any need of tucking or crotchet, tongue or pusher needles whatsoever and also without any meshing or crotcheting of the weft thread being needed. These weaving devices as standard on more complicated means of prior art can now all be eliminated by application of the method in accordance with the invention. Merely weft holdbacks in contact with the usual control of catch needle holders are still needed.
An advantageous further embodiment of the method in accordance with the invention for weaving a seat belt webbing comprising an inner portion, a preferably soft right-hand edge portion and a preferably soft left-hand edge portion, is characterized by a continuous repeat of a first step sequence;    ar) picking the right-hand weft thread from the right-hand side of the webbing into the right-hand edge portion and into the inner portion by means of a right-hand weft needle,    al) picking the left-hand weft thread from the left-hand side of the seat belt webbing into the left-hand edge portion and into the inner portion by means of a left-hand weft needle simultaneously to step ar),    br) retaining the right-hand weft thread in the transition portion from the inner portion to the left-hand edge portion by means of a left-hand weft holdback,    bl) retaining the left-hand weft thread in the transition portion from the inner portion to the right-hand edge portion by means of a right-hand weft holdback simultaneously to step br),    cr) tucking the right-hand weft thread with the left-hand weft holdback and returning the left-hand weft holdback to the fell,    cl) tucking the left-hand weft thread with the right-hand weft holdback and returning the right-hand weft holdback to the fell simultaneously to step cr),    dr) returning the right-hand weft needle to the right-hand side of the seat belt webbing,    dl) returning the left-hand weft needle to the left-hand side of the seat belt webbing simultaneously to step cr),    e) stripping off the weft loops formed in the previous step from the two weft holdbacks by the reed to the fell and forwarding the two weft holdbacks away from the fell,    f) beating the two weft threads by a reed.The method is advantageously characterized in that two weft needles guiding the weft threads each coming from the right and left weft picking side respectively pick the weft threads simultaneously and practically symmetrically transversely over the webbing, each of which is held back on the opposite side in the transition between the inner portion and edge portion by the weft holdback element located there in each case, after which the weft needles are returned to their side entraining and tensioning the weft threads tensioned until the reed beats up the newly inserted weft threads to the already woven webbing material. Up until this point in time the weft threads held back by the weft holdbacks are beat up and set by the following shed change.
In application of the method in accordance with the invention as it reads from claim 2 both weft threads are arranged in the inner portion, and only one in each case being in the edge portion belonging to its weft thread picking side. This results in the advantage that each edge portion is occupied only with one weft thread and is thus softer, whilst the two weft threads in the inner portion endow it with a higher transverse stiffness due to twice the proportion of material as compared to the edge portions.
Another advantageous further embodiment of the method for weaving a seat belt webbing whose right and left-hand weft threads are hybrid threads is characterized by the following step implemented after weaving: thermosetting the seat belt webbing. Used as weft threads in this arrangement are hybrid threads as are converted after weaving by said thermosetting into monofil-type structures in endowing the seat belt webbing in accordance with the invention with additional monofil qualities adequately for transverse stiffness without making use of actual monofil threads. Hybrid threads are threads made of materials having different melting temperatures as are known from prior art. The advantage in this is that after weaving such hybrid threads as weft threads, as claimed herein, the hybrid threads can be solidified into a monofil condition by subjecting them to thermosetting after weaving, resulting in the components of the hybrid threads having a low melting point to melt embedding the components having a higher melting point into monofil type structures featuring enhanced flexibility, transverse stiffness and as termed with seat belt webbing, rebound transversely to the webbing.
A further advantageous aspect of the method in accordance with the invention is the use an additional left-hand weft needle for picking a monofil weft needle supplied in the transition between the left-hand edge portion and the inner portion, the monofil weft needle being held secure on both sides in addition to the just mentioned weft threads likewise by the weft holdbacks resulting in the monofil weft threads being woven only in the inner portion. This is characterized by the following further steps:    az) picking a monofil weft thread fed preferably in the transition portion from the inner portion to the left-hand edge portion from left to right up to the transition portion from the inner portion to the right-hand edge portion by means of a supplementary weft needle simultaneously to step ar)    bz) retaining the monofil weft thread in the transition portion from the inner portion to the right-hand edge portion by means of the right-hand weft holdback simultaneously to step cr),    cz) tucking the monofil weft thread with the right-hand weft holdback and returning the right-hand weft holdback up to just before the fell simultaneously to the step cr)    dz) returning the supplementary weft needle simultaneously to step dr).Catching, releasing and beating the monofil weft thread is done analogous to the actions as already described relating to the weft threads as described above, for which, as explained further on in the description, an additional weft needle is employed. The supplementary monofil weft thread additionally incorporated in the inner portion in accordance with the invention results in the advantage that the seat belt webbing now features enhanced transverse stiffness in the inner portion whilst the edge portions remain soft as wanted.
A further advantageous embodiment of the method in accordance with the invention for weaving a webbing is characterized by the following second sequence in the steps optionally alternated with the first sequence of steps as it reads from claim 2 for optionally forming picots at the selvedges of the webbing:    apr) picking the right-hand weft thread from the right-hand side of the webbing over the full webbing width beyond the left-hand webbing side by means of a right-hand weft needle),    apl) picking the left-hand weft thread from the left-hand side of the webbing over the full webbing width beyond the right-hand webbing side by means of a left-hand weft needle, simultaneously to step apr),    bpr) retaining the right-hand weft thread outside of the webbing adjoining the left-hand edge portion by means of a second left-hand weft holdback in forming weft loops,    bpl) retaining the left-hand weft thread outside of the webbing adjoining the right-hand edge portion by means of a second right-hand weft holdback in forming weft loops simultaneously to step bpr),    dr) returning the right-hand weft needle to the right-hand side of the seat belt webbing,    dl) returning the left-hand weft needle to the left-hand side of the seat belt webbing simultaneously to step dr),    ep) stripping off the weft loops formed in the steps bpr) and bpl) from the two weft holdbacks,    f) beating the two weft threads by a reed.This now makes it possible to produce webbing with weft loops or so-called picots optionally included to protrude beyond the selvedge which is particularly favorable in the production of ribbons and braids, mainly for ready-to wear garments. Involved in this is also a further advantageous embodiment of the method in accordance with the invention which is characterized by elastic warp threads being made use of.
In another advantageous further embodiment of the method in accordance with the invention multifil threads are employed as weft threads to guarantee a soft selvedge. As a rule multifil threads are also employed as warp threads for seat belt webbing, resulting in the wanted soft selvedge of advantage in the edge portions. In another advantageous further embodiment of the method in accordance with the invention elastic threads are employed. This now makes it possible to produce elastic webbings for ready-to wear garments.
The object is furthermore achieved by a narrow fabric needle loom as it reads from claim 9 featuring a right-hand weft needle and a left-hand weft needle configured controllably simultaneously to each other, as well as a right-hand and a left-hand weft holdback for retaining and releasing the left-hand and right-hand weft thread respectively, and also being configured to work coordinated to each other, particularly working simultaneously with each other, and a reed. In a further advantageous aspect of the invention the narrow fabric needle loom is characterized in that the weft holdbacks are fixedly secured to the loom and that an elastic arrangement of stripper/holder wires is provided oriented preferably slightly towards the fell suitable for stripping off the weft thread loops before the shed change and before the fell from the weft holdbacks and retaining same by urging them to the fell until the reed itself beats up the weft threads. In this arrangement the narrow fabric needle loom in accordance with the invention may be additionally characterized in that the weft holdbacks are configured vertically pliant so that they are easily lifted by the tensioned weft threads in facilitating the sliding down of the weft threads.
With the narrow fabric needle loom in accordance with the invention the method in accordance with the invention for producing a seat belt webbing in accordance with the invention fabrication is now much simpler and with less wear and tear as is known in prior art. No catchment threads and no blocking threads now being needed to produce soft edges, this also eliminating the need for all of the equipment needed for this purpose in prior art. This greatly simplifies producing the seat belt webbing as compared to methods and devices as known from prior art. When employing hybrid threads as the weft threads thermosetting is done after weaving which, however, adds nothing to costs of the method as compared to prior art since any seat belt webbing, even when not made of hybrid weft threads, requires thermosetting to endow the seat belt webbing with the necessary shrinkage and stretch together with the wanted buffer for stretching thereof. Further advantages and features read from the sub-claims.